1. Field of the Invention
This invention relates generally to a rolling contact bearing assembly, and, in particular, to a structure for mounting an attachment to such a rolling contact bearing assembly. More specifically, the present invention relates to a structure for mounting a fixture member, such as an attachment, to a body of a linear motion rolling contact bearing assembly including a bed and a table which are both structured to have a U-shaped cross section from a thin steel plate and which are assembled with rolling members interposed therebetween thereby allowing motion relative to each other.
2. Description of the Prior Art
A linear motion rolling contact bearing assembly is well known in the art, and it generally comprises a bed (or rail), a table (or slider) and a plurality of rolling members interposed between the bed and the table to be in rolling contact with opposed guide grooves formed in the bed and the table. Thus, a relative motion is provided between the bed and the table through the rolling members, so that the table can move along the bed slidingly in a reciprocating manner. The bed is generally constructed in the form of a straight rail having a U-shaped cross section from a thin steel plate, and, similarly, the table is also constructed to have a U-shaped cross section from a thin steel plate so that the table straddles the bed when assembled. Since a relative linear motion is provided between the bed and the table with a minimum of resistive force mainly due to friction, this linear motion rolling contact bearing assembly finds many applications in various fields, such as machine tools and robots in manufacturing or assembly lines for various products.
When such a linear motion rolling contact bearing assembly is used in various fields of application, a fixture member or attachment must be mounted on the bearing assembly to transmit the relative motion to other components. For this purpose, either one or both of the bed and the table is typically provided with a hole, threaded or unthreaded, and the attachment is fixedly mounted on the bearing assembly by means of a bolt. FIG. 6 shows one prior art example in which an attachment member 7 is fixedly attached to a table 1 or bed 2 of such a linear motion rolling contact bearing assembly by means of a bolt. In this case, the attachment member 7 is provided with a through-hole and the table 1 or bed 2 is provided with a threaded hole and a bolt is screwed into the threaded hole provided in the table 1 or bed 2 to have the attachment member 7 fixedly attached to the table 1 or bed 2. With this structure, however, since the table 1 or bed 2 is comprised of a relatively thin steel plate, it becomes deformed when the bolt is tightened as indicated by the solid line after tightening and the one-dotted line before tightening. In this case, the table 1 or bed 2 becomes somewhat warped after tightening so that an error in position indicated by l occurs at a certain point after tightening.
FIG. 10 shows another typical prior art structure for affixing the attachment member 7 to the table 1 or bed 2 of the linear motion rolling contact bearing assembly, and, in this case, which is a reverse of the case shown in FIG. 6, the attachment member 7 is provided with a threaded hole and the table 1 or bed 2 is provided with a through-hole, wherein a bolt 9 is screwed into the threaded hole of the attachment member 7 for having the attachment member 7 fixedly attached to the table 1 or bed 2. Also in this case, the table 1 or bed 2 is deformed after tightening the bolt 7. If the table 1 or bed 2 is deformed due to tightening of the bolt 9 for fixed mounting of the attachment member 7, the opposed guide grooves formed on the opposed surfaces of the table 1 and the bed 2 are misaligned, which then would increase the resistive force against the relative motion between the table 1 and the bed 2. Thus, such a deformation of the table 1 or bed 2 is disadvantageous because a smooth relative motion between the table 1 and the bed 2 is impaired.